A123934 Triangle T(n,k), 1<=k<=n :forms the odd-indexed trinomial coefficients (A027907).

1, 2, 2, 3, 7, 3, 4, 16, 16, 4, 5, 30, 51, 30, 5, 6, 50, 126, 126, 50, 6, 7, 77, 266, 393, 266, 77, 7

Offset: 1

Author

Philippe Deléham, Oct 30 2006

Keywords

• nonn
• tabl

Examples

			Triangle begins:
1;
2, 2;
3, 7, 3;
4, 16, 16, 4;
5, 30, 51, 30, 5;
6, 50, 126, 126, 50, 6;
7, 77, 266, 393, 266, 77, 7;
		

Crossrefs

Cf. A056241.

Formula

Sum_{k, 1<=k<=n}T(n,k)=A003462(n)=(3^n-1)/2.